1. Field of the Invention
This invention defines a new and improved style of motorcycle suspension system to be used on motorcycles that use swing-arm type suspension systems.
2. Description of the Prior Art
The use of air-bags in suspension systems for Harley Davidson(copyright) type of motorcycles is known in the prior art.
The Harley Davidson(copyright) SOFTAIL(copyright) motorcycle suspension system uses a swing arm that is pivotally attached to the struts of the motorcycle main frame. This allows the rear wheel assembly to move independently from the frame about a singular pivot point. The swing arm rotates about a pivot and allows the wheel to move in an arcuate motion. The swing arm has a pair of wheel mounts that are positioned and spaced to mount a wheel assembly and provide proper orientation and location for the wheel relative to the motorcycle. The swing arm has a pair of supports at each wheel mount, each pair are positioned in a plane and radiate from the wheel mount to a support member that connects the pair of supports in a planar like orientation. Transverse bars, or cross members link each of the wheel mounts an upper location and a lower location providing proper spacing and structural rigidity for the swing arm. At an intermediate position, positioned between the upper and lower cross members, an additional transverse bar or cross member links each wheel mount. The intermediate cross member is tubular, and provides an axis for the swing arm to rotate about. Each of the support members have a hole that coincides with the tubular shaped cross member, providing a through-hole for pivot bolts to be inserted therethrough. Each support member is positioned adjacent to, and located inside the frame and are therefore hidden by the main frame struts, giving the illusion of a motorcycle having no visible suspension system.
The standard or stock SOFTAIL(copyright) motorcycles uses a suspension system that incorporates two shock absorbers that are positioned in a parallel relationship to each other and are orientated so the longitudinal axis of the shock absorbers is parallel to the direction of travel of the motorcycle. One end of each of the shock absorbers is attached to the main frame. The other end of each of the shock absorbers is connected to a member that extends forward from the lower cross member of the swing arm. The main frame of the motorcycle hides the shock mounts from view, maintaining the appearance of the SOFTAIL(copyright) motorcycle.
The problem with existing suspension systems for the SOFTAIL(copyright) motorcycles is that the relative arcuate travel of the swing arm is usually greater than the allowable travel of the shock absorbers. This results in a harsh ride, since the current state of shock absorbers precludes rapid change in direction due to the fluid in the shock absorber (internal drag), as well as inertial drag caused by the action of the shock absorber.
U.S. Pat. No. 6,003,628 (hereinafter the 628 patent) describes the use of an airbag as a replacement for the spring in the coil-over shock used in standard Harley Davidson(copyright) SOFTAIL(copyright) motorcycles. The 628 patent describes the use of at least one elastomeric air bag that is housed within a slideable housing, where one end is attached to the main frame of the motorcycle and is pivotally attached at it""s rear position to the lower cross member of the swing arm. Slide rods are also attached to the forward portion of the slideable housing and are allowed to slide within a pair of bushings. As the swing arm moves upward in its arcuate motion, the slideable air bag housing is drawn rearward, causing the slide bars to draw the housing rearward, compressing the air bags. Opposing motion causes the slide bars to push the housing forward, extending the air bags. The air bags are adjustable using an air compressor mounted on the motorcycle to regulate the ride height, which also regulates the harshness of the ride.
The main problem with the 628 design is the inherent complexity of the sliding mechanism. The mechanism requires a reversal of the action of the swing arm in order to provide for the correct translation of the mechanism which will result in a compression of the air bag springs, and on reversal extension of the air bags. Additionally, the preferred embodiment of the invention advises the elimination of the shock absorber, which tends to allow the suspension to oscillate in its arcuate motion without any damping, resulting in an undesirable ride.
The suspension system of a Harley Davidson(copyright) SOFTAIL(copyright) motorcycle consists of a main frame, and a swing arm that is pivotably mounted about a longitudinal axis to the main frame. A front bag bracket is fixed to the main frame, and has a hole that allows a swing arm axis tube that penetrates the front air bag bracket and positions the front air bracket relative to the longitudinal axis. A rear bag bracket permits the swing arm axis tube to pivot about the longitudinal axis. The rear bag bracket is attached to a shock absorber and the swing arm at the lower portion of the bracket and arcuately travels with the swing arm in its relative motion. An air bag is attached between the front bag bracket and the rear bag bracket and by inflating the air bag, raises the ride height of the motorcycle. Conversely, deflating the air bag lowers the ride height of the motorcycle. The air bag is connected to an air compressor, where the air compressor has a means to regulate inflation and deflation of the airbag by the driver.
In the preferred embodiment, inflation of the airbag causes a scissors like motion between the front air bracket and the rear air bracket where the air bag compresses when weight is applied to the motorcycle. The air bag suspension acts like a standard automotive type spring and shock system, which will greatly improve the ride of the motorcycle on all types of terrain.
It is an object of the invention to create a suspension system that will not require modification of components of the existing Harley Davidson(copyright) SOFTAIL(copyright) mainframe or swing arm.
It is another object of the invention to allow easy regulation of the ride height and ride stiffness of the motorcycle while either stationary or being driven.
Other objects, advantages, and novel features of the present invention will be come apparent from the following detailed description of the invention when considered in conjunction with the drawings accompanying the patent.